It is known that polyphase rotary electrical machines have advantages over three-phase machines in terms of reduction of the oscillations of the torque in motor mode, or ease of elimination of the harmonics in generator mode.
The performance of the polyphase machines is also increased. For example, the stator losses of a hexaphase machine can be close to 7% less than those of an equivalent three-phase machine.
However, the increase in the number of phases gives rise to an increase in the number of current sensors which are necessary in order to control the machine, since a sensor is a priori necessary in order to measure each independent current variable. Since the sum of all the intensities is zero, the number of sensors necessary is equal to the number of phases less one, i.e. five sensors in the case of a hexaphase machine.
A double-three-phase structure makes it possible to reduce the number of sensors, and makes possible various optimisations of a mechatronic type relating to the architecture of the electronic power modules which are connected to the stator of the machine.
In particular, in the architecture disclosed in patent application FR2967845 by the company VALEO EQUIPEMENTS ELECTRIQUES MOTEUR, each electronic power module comprises power semiconductors corresponding to two branches of a hexaphase bridge, i.e. with two phases, which makes possible a reduction of the size, and facilitates the integration of the modules on a rear bearing of the machine.
For the purpose of applications in the highly competitive motor vehicle industry, the objective of the present invention is to obtain a rotary electrical machine with the best possible performance, with electronic components with a fixed cost, and therefore with predetermined characteristics for this cost.
When the machine is stopped or is rotating at a very low speed, the inventive body has found points of heating of the electronic power modules which are liable to give rise to an avalanche phenomenon, and to destroy the semiconductors.